ISSN:
1432-1424
Keywords:
pancreas
;
Ca2+ pools
;
Ca2+ pump
;
acini
;
saponin
;
secretagogue
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Intracellular ATP-dependent Ca2+ sequestration mechanisms were studied in isolated dispersed rat pancreatic acini following treatment with saponin or digitonin to disrupt their plasma membranes. In the presence of45Ca2+ concentrations 〈10−6 mol/liter, addition of 5 mmol/liter ATP caused a rapid increase in45Ca2+ uptake exceeding the control by fivefold. ADP mimicked the ATP effect by 50 to 60%, whereas other nucleotides such as AMP-PNP, AMP-PCP, CTP, UTP, ITP, GTP, cAMP and cGMP did not. Maximal ATP-promoted Ca2+ uptake was obtained at 10−5 mol/liter Ca2+ uptake by mitochondrial inhibitors was dependent on the Ca2+ concentration, indicating the presence of different Ca2+ storage systems. Whereas the apparent half-saturation constant found for mitochondrial Ca2+ uptake was ∼4.5×10−7 mol/liter, in the presence of antimycin and oligomycin (nonmitochondrial uptake) it was ∼1.4×10−8 mol/liter. In the absence of Mg2+ both ATP- and ADP-promoted Ca2+ uptake was nearly abolished. The Ca2+ ionophore and mersalyl blocked Ca2+ uptake. Electron microscopy showed electrondense precipitates in the rough endoplasmic reticulum of saponintreated cells in the presence of Ca2+, oxalate and ATP, which were absent in intact cells and in saponin-cells without ATP or pretreated with A23187. The data suggest the presence of mitochondrial and nonmitochondrial ATP-dependent Ca2+ storage systems in pancreatic acini. The latter is likely to be located in the rough endoplasmic reticulum.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01869964
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